Post-frontal rain and snow showers gradually decrease as the day progresses on Sunday. Temperatures are milder behind the front, so moderate W ridgeline winds will bring 4500 ft snow levels into areas near and east of the Cascade Crest as the day progresses, overwhelming the stubborn E flow. This milder air is unlikely to be accompanied by precipitation for areas more than 5 miles east of the Crest. The bulk of the light postfrontal shower activity should occur southward from the mountain loop with locally moderate intensity. All shower activity eases during the afternoon.
A low moving ESE into Oregon Sunday night will bring a period of light rain and snow. Models indicate that the northward extent will be around the Washington/Oregon border. We'll monitor for the potential of moderate precipitation around Mt Hood, but the system comes in with generally light ESE winds and minimal dynamic support. Most of the light precipitation should exit the area by Monday afternoon. Sunshine should increase across Washington from N to S on Monday. Light E flow brings a cool start to areas east of the Cascade Crest. Areas further west should experience more impacts of the offshore high pressure as freezing levels rise to Cascade Crest level in the afternoon.
Weather Forecast
Olympics
West North
West Central
West South
Stevens Pass
Snoqualmie Pass
East North
East Central
East South
Mt. Hood
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Sunday
A few light rain or snow showers, then mostly cloudy skies with mid-level clouds in the afternoon. Mild.
Sunday
Night
Mostly cloudy.
Sunday
A few rain or snow showers in the morning, then mostly cloudy skies in the afternoon.
Sunday
Night
Partly cloudy.
Sunday
Light rain and snow showers decrease or end during the afternoon. Mild.
Sunday
Night
Mostly cloudy.
Sunday
Decreasing light rain and snow showers, heaviest at Paradise. Decreasing light to moderate ridgeline winds. Mild.
Sunday
Night
Cloudy in the evening with a chance of light rain or snow overnight, primarily for the southern parts.
Sunday
Decreasing light rain or snow showers with a chance for weak convergence. Decreasing light ridgeline and light E or variable wind at the Pass.
Sunday
Night
Mostly cloudy. Light ridgeline and E wind at the Pass.
Sunday
Moderate right rain or snow showers and weak convergence become light and taper during the afternoon. Rising snow levels. Decreasing light to moderate ridgeline and light E or variable wind at the Pass.
Sunday
Night
Cloudy with a few rain or snow showers early. Light ridgeline and E wind at the Pass.
Sunday
A few rain or snow showers early, then becoming partly cloudy. Moderating temperatures.
Sunday
Night
Partly cloudy.
Sunday
Mostly cloudy with convergence spillover or light rain and snow showers decreasing closer to the Cascade Crest. Otherwise, mostly cloudy skies with decreasing light to moderate ridgeline winds.
Sunday
Night
Mostly cloudy.
Sunday
Decreasing light rain and snow showers confined to areas near the Cascade Crest.
Sunday
Night
Cloudy.
Sunday
Decreasing mostly light rain and snow showers focus increasingly on western slopes of Mt Hood. Strong ridgeline winds early gradually decrease into the moderate range.
The NWAC program is administered by the USDA-Forest Service and operates from the National Weather Service Forecast Office in Seattle. NWAC services are made possible by important collaboration and support from a wide variety of federal, state and private cooperators.
The 5000’ temperature forecast does not imply a trend over the 12 hr period and only represents the max and min temperatures within a 12 hr period in the zone. The 6-hr snow level forecast, the forecast discussion, and weather forecast sections may add detail regarding temperature trends.
The snow level forecast represents the general snow level over a 6 hr time period. Freezing levels are forecast when precipitation is not expected.
*Easterly or offshore flow is highlighted with an asterisk when we expect relatively cool east winds in the major Cascade Passes. Easterly flow will often lead to temperature inversions and is a key variable for forecasting precipitation type in the Cascade Passes. Strong easterly flow events can affect terrain on a more regional scale.
Ridgeline winds are the average wind speed and direction over a 6 hr time period.
The wind forecast represents an elevation range instead of a single elevation slice. The elevation range overlaps with the near and above treeline elevation bands in the avalanche forecast and differs per zone.
Wind direction indicates the direction the wind originates or comes from on the 16-point compass rose.
Water Equivalent (WE) is the liquid water equivalent of all precipitation types; rain, snow, ice pellets, etc., forecast to the hundredth of an inch at specific locations. To use WE as a proxy for snowfall amounts, start with a snow to water ratio of 10:1 (10 inches of snow = 1 inch WE). Temperatures at or near freezing will generally have a lower ratio (heavy wet snow) and very cold temperatures can have a much higher ratio (dry fluffy snow).